A gear bearing is a mechanical structure comprising both gear and roller bearing surfaces such that the mechanical power structure and bearing motion control functions are performed without the need for dedicated bearings. Gear bearings take both component and device forms. Gear bearing components can be constructed in many forms, and gear bearing components can be directly interfaced to each other as modules to form gear bearing devices. Gear bearing devices use rolling friction throughout, so external bearings are not required. Epicyclical gear bearing speed reducers are easily constructed using gear bearing technology and these provide good speed reduction in a compact package. “Rock Lock” (based on force balancing) properties are inherent in gear bearing epicyclical speed reducers and these ensure exceptional safety by preventing joint back drive (when the gear bearing reduction ratio is above a certain value, around 90-120:1). Gear bearings use the gear tooth tips mated against the roller bearing to lock the system axially. In addition to locking the system together this mate can perform thrust bearing functions, adding additional functionality to the mechanism. Gear bearing devices can be made to provide exceptional bearing strength in a compact package and have unique motion control properties, which enable them to perform competitive edge functions.
A gear bearing system is described in U.S. Pat. No. 6,626,792. This system utilizes a planetary gear arrangement that eliminates conventional bearings by placing a contact surface at each gear's pitch diameter. The system utilizes a one-tooth difference between input and output pinion gears. The contacting surfaces maintain proper meshing and allow the gear set to operate with minimal vibration. Reliability is also increased due to the decrease in part count and overall complexity. Also inherent to the gear bearing design is the ability to achieve a large range of gear ratios using the same mechanisms, for example, from 1:1 to 1:2000 by only changing the number of teeth of each gear. The gear bearing system in this patent includes a single roller per gear that locks the system together using the ends of the gear teeth.
Other known drive systems utilize planetary gear systems with helical planetary gears and ball bearings and that drive an output off a carrier. Harmonic drives, that operate using a wave generator, are also known. A brief description can be found in US Patent Publication No. 2006/0073922.
Regarding the field of prosthetic devices, body-powered components have been used in prosthetics for centuries and are still commonly prescribed today. Control of these systems involves coordination of gross body movements, remote from the amputation site, and generally include some type of body harness attached directly to the prosthesis. While these prostheses are generally lightweight and low-cost, they do have significant disadvantages. The body harness generally restricts the work envelope, and the amputee must be able to coordinate body motions in a synchronized manner to properly operate the terminal device. Higher level amputees are often unable to generate sufficient motion in order to properly activate the prosthesis. Achieving satisfactory grip strength is also difficult due to the mechanical limitations of currently available terminal devices and grasp patterns.
Externally powered components have been used since the late 1970s and offer some distinct advantages over body powered components. Electronic elbows can produce around 15 lbs/ft lifting power and electronic terminal devices can produce a maximum grip force of approximately 22 lbs. While offering improved performance over many body powered components, these devices are still inadequate for many tasks.